As requirements for the reliability and the throughput of a wireless communication are increasing, solutions and methods for providing high data rate cellular access with high quality-of-service are needed. Especially in certain environments, such as indoor environments, the transmitted data suffers from multiple penetrations before a terminal device receives it. These penetrations decrease the power of the transmitted data signal and affect the data rate and quality of the received data. Examples of such indoor propagation environments where the required data rate is high include office buildings and airport halls.
It has been proposed to cover such environments with a distributed antenna system (DAS), where instead of covering an area 100 by only one base station 102 (or Node B as specified in the E-UTRAN (Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network)) as depicted in FIG. 1A, the same coverage 100 is provided by multiple remote antenna units (RAU) 104A-104D controlled by a base station 106 as illustrated in FIG. 1B. In other words, a DAS is a network where spatially separated antenna nodes or RAUs are connected to a common source via a transport medium. A DAS commonly uses a fiber cable within buildings to actively distribute signals to a network of low-power antennas. A DAS network may thus provide wireless service within a geographical area or structure. The advantages of the DAS include for example improved reliability, reduced total power, possibility of increased capacity and more frequently occurring line-of-sight (LoS) condition between the RAU and the terminal device.
Generally, when new cells or base stations are introduced to a cellular access system, they need to be configured in order to enable efficient and reliable communication between them and the terminal devices. The configuration includes, for example, providing each base station with a specific cell identifier, which may be a global cell identifier (GCID) or a physical layer cell identifier (PLCID). For example in E-UTRAN, the base station in the broadcast system information broadcasts the GCID. The PLCID, on the other hand, is an essential configuration parameter defining a cell reference signal sequence broadcast by the base station on a synchronization channel, and a mobile station identifies the base station from the signal sequence upon obtaining synchronization with the base station. In E-UTRAN the PLCID corresponds to a unique combination of one orthogonal sequence and one pseudo-random sequence, thereby resulting in a total number of 504 unique PLCIDs and expected reuse of the PLCIDs in different cell locations of a cellular radio access network. The use of identical PLCIDs by two spatially overlapping cells may cause severe identity and interference problems, which disturb the network operation.
Similarly, with the introduction of a DAS to an ITU IMT-A (International Telecommunication Union International Mobile Telecommunications-Advanced) cellular system or a similar system, such as the E-UTRAN, the activated base stations need to be configured. Since one base station controls multiple RAUs in the DAS, novel methods that enable dynamic configuration are desired.